A receiving circuit (10) includes an amplifier (15) which amplifies receiving signals (SP, SN) of a piezoelectric sensor (2), and a plurality of transistors (11a, 11b) or (12a, 12b), which are connected in parallel to between one end of the piezoelectric sensor (2) and one end of the amplifier (15), and are turned on with phase shift when switching is performed to receiving operations.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A receiving circuit comprising: an amplifier for amplifying a reception signal of a piezoelectric sensor; and a plurality of transistors connected in parallel between one end of the piezoelectric sensor and one end of the amplifier, the transistors being turned on with phase shift in switching to a reception operation.
2. The receiving circuit according to claim 1 , wherein the plurality of transistors are 2n transistors obtained by dividing a single transistor having desired impedance characteristics into ½n (n is a natural number).
3. The receiving circuit according to claim 2 , wherein the 2n transistors are turned on with phases shifted by T/2n each (T is a resonance period of the piezoelectric sensor) in switching to the reception operation.
4. The receiving circuit according to claim 1 , further comprising a filter for blunting a control signal of each transistor.
5. The receiving circuit according to claim 1 , wherein the reception signal is transmitted between the piezoelectric sensor and the amplifier in a differential form.
6. The receiving circuit according to claim 5 , further comprising a switch for short-circuiting a positive phase transmission path and a reverse phase transmission path of the reception signal in switching to the reception operation.
7. A receiving circuit comprising: an amplifier for differentially amplifying a reception signal of a piezoelectric sensor; a first transistor for connecting between the piezoelectric sensor and the amplifier in switching to a reception operation; and a second transistor for short-circuiting a positive phase transmission path and a reverse phase transmission path of the reception signal in switching to the reception operation.
8. A receiving circuit comprising: an amplifier for amplifying a reception signal of the piezoelectric sensor; a main transistor connected between one end of the piezoelectric sensor and one end of the amplifier, the main transistor being turned on in switching to a reception operation; and a sub transistor connected in parallel to the main transistor, the sub transistor having a larger on-impedance than the main transistor and being turned on prior to the main transistor in switching to the reception operation.
9. The receiving circuit according to claim 8 , the main transistor is divided into 2n transistors to be turned on with phases shifted by T/2n each (T is a resonance period of the piezoelectric sensor, and n is a natural number) in switching to the reception operation.
10. The receiving circuit according to claim 8 , further comprising a filter for blunting control signals of the main transistor and the sub transistor.
11. The receiving circuit according to claim 8 , wherein the reception signal is transmitted between the piezoelectric sensor and the amplifier in a differential form.
12. The receiving circuit according to claim 11 , further comprising a switch for short-circuiting a positive phase transmission path and a reverse phase transmission path of the reception signal in switching to the reception operation.
13. A semiconductor device, comprising the receiving circuit according to claim 1 , to which the reception signal is input from the piezoelectric sensor.
14. The semiconductor device according to claim 13 , further comprising: a transmission circuit configured to output a transmission signal to the piezoelectric sensor; and a control circuit configured to control the reception operation of the receiving circuit and the transmission operation of the transmission circuit in a time sharing manner.
15. The semiconductor device according to claim 14 , wherein the transmission circuit is disposed for each one of a plurality of piezoelectric sensors, and the receiving circuit is disposed solely for the plurality of piezoelectric sensors.
16. The semiconductor device according to claim 11 , wherein a plurality of signal paths respectively connecting between the receiving circuit and the plurality of piezoelectric sensors are designed to have the same length.
17. A sensor device comprising a piezoelectric sensor and the semiconductor device according to claim 13 .
18. The sensor device according to claim 17 , wherein the sensor device is a current meter for measuring flow speed of a fluid flowing in a pipe.
19. The sensor device according to claim 18 , wherein the piezoelectric sensor includes a first piezoelectric sensor and a second piezoelectric sensor disposed on an inner wall surface of the pipe in such a manner to be opposed to each other with a predetermined angle to the fluid.
20. The receiving circuit according to claim 9 , further comprising a filter for blunting control signals of the main transistor and the sub transistor.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
August 31, 2012
August 30, 2016
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